Off locking trigger switches

ABSTRACT

A trigger switch for portable tools such as circular saws and the like having a return-spring biased trigger that is actuated by the forefinger of the user to turn the tool on and upon release returns to off position under spring action. The trigger is provided with a built-in spring biased lock that automatically locks the trigger in its off position whenever the trigger returns thereto. A manual release button is arranged to be pressed by the thumb of the user to release the lock and allow reactuation of the trigger. Two versions of off lock are shown for in-line (linearly movable) trigger and a third version is shown for an overhanging (pivoted) trigger.

United States Patent Drummer Assignee:

US. Cl 200/157, 200/169 PB, 173/710 Int. Cl. H0lh 13/08, HOlh 9/20 Field of Search 200/157, 169 PB,

ZOO/42 R; 173/710; 310/68 A [56] References Cited UNITED STATES PATENTS 3,662,136 5/1972 Bienwald et a1. 200/157 3,132,227 5/1964 Butler 200/157 FOREIGN PATENTS OR APPLICATIONS 1,263,901 3/1968 Germany 200/169 PB [451 July 17, 1973 Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A. Vanderhye Attorney-Hugh R. Rather et a1.

[ ABSTRACT A trigger switch for portable tools such as circular saws and the like having a return-spring biased trigger that is actuated by the forefinger of the user to turn the tool on and upon release returns to off position under spring action. The trigger is provided with a built-in spring biased lock that automatically locks the trigger in its off position whenever the trigger returns thereto. A manual release button is arranged to be pressed by the thumb of the user to release the lock and allow reactuation of the trigger. Two versions of off lock are shown for in-line (linearly movable) trigger and a third version is shown for an overhanging (pivoted) trigger.

8 Claims, 13 Drawing Figures 'llill Patented July 17, 1973- 3 Sheets-Sheet 1 Patented July 17, 1973 3,746,815

3 Sheets- Sheet 2 Patented July 17, 1973 3,746,815

3 Sheets-Sheet 3 BACKGROUND OF THE INVENTION Off locks for trigger switches have been known heretofore. These prior off locks are characterized primarily by laterally slidable pins or rotary knobs which in one position engage an abutment on the tool handle to prevent trigger movement and in another position are clear of such abutment to allow trigger movement. Manual actuation is required for setting thereof in either position. Also such prior locks are not built into the trigger switch but involve mounting of parts within and cooperation with parts of the tool handle.

While such prior off locks have been useful for their intended purpose, this invention relates to improvements thereover.

SUMMARY OF THE INVENTION This invention relates to off locking trigger switches for portable tools and more particularly to automatically-engaging, manual-release off locking in-line and overhanging trigger switches.

An object of the invention is to provide an improved off locking trigger switch.

A more specific object of the invention is to provide an improved off lock for a trigger switch that automatically engages to prevent accidental starting of the portable tool.

Another specific object of the invention is to provide a self-contained trigger switch having a built-in off lock therein.

Another specific object of the invention is to provide a self-contained trigger switch having an automaticallyengaging, manual-release off lock incorporated therein.

Other objects and advantages of the invention will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged isometric view of a first embodiment of an off locking trigger switch of the in-line type;

FIG. 2 is a left side elevational view thereof;

FIG. 3 is a fragmentary cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4. is a fragmentary cross-sectional view taken along line 4-4 of FIG. 3.

FlG. 5 is a top view thereof with the upper part of the frame removed; and

FIG. 6 is an isometric view of the leaf spring locking lever thereof. v

FIG. 7 is an enlarged left side elevational view of a second embodiment of an off locking trigger switch of the in-line type;

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7; and

FIG. 9 is an isometric view of the locking member thereof.

FIG. 10 is an enlarged left side elevational view of a third embodiment of an off locking trigger switch, this being of the overhanging trigger type;

FIG. 11 is a right end view thereof according to FIG. 10 but with some of the parts left out to better show the locking mechanism;

FIG. 12 is an exploded isometric view of the trigger and locking parts thereof; and

FIG. 13 is a cross-sectional view taken along line 13-13 of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is shown an off locking trigger switch of the in-line type constructed in accordance with the invention. In-line type refers to the linear sliding movement of the trigger. This switch comprises an insulating base 2 housing the switch contacts, or speed control circuit and switch contacts, as desired. This base normally has holes in the bottom through which conductors extend or through which conductors may be inserted for connecting the trigger switch to an external circuit. The base has an open top through which switch actuation takes place.

A trigger 4 of the in-line type has a finger-engaging portion 4a and a slidable portion 4b, the latter portion overlying the base and being held on the base by a frame 6 usually made of metal or molded insulating material. A helical compression spring 8 shown in FIG. 4 biases the trigger into its forwardly extended off position and the trigger may be depressed by the forefinger of the user against the force of this return spring 8 into its on (contact closed) position.

As shown in FIGS. 1 and 2, frame 6 is provided with a pair of rectangular apertures 6a at its top to limit the trigger movement in opposite directions. Extending up through these apertures are respective projections 4c integrally molded on the upper surface of slidable portion 4b of the trigger. As will be apparent, these projections stop against the forward end of these apertures when the trigger is in its off position and stop against the rear end of the apertures when the trigger is depressed into its fully on position.

A detent for trigger positioning purposes may be provided by a spring-biased steel ball 10 sunk into a round well 4d in the upper surface of the slidable portion 4b and a pair of holes 6b in the frame. As will be apparent, ball 10 enters the forward hole in the off position of the trigger and enters the rear hole in the on position of the trigger to provide feel.

As shown in FIGS. 3 and 4, the slidable portion of the trigger is provided with a groove 4e for accommodating return spring 8. One end of this return spring abuts the forward end wall of this groove and the other end abuts the frame.

The off locking mechanism comprises a leaf spring locking lever 14, most clearly shown in FIG. 6, and a locking hole 6c in the left side of the frame.

The locking lever is mounted on the trigger. For this purpose the trigger is provided at its left side with a slot having its greatest depth portion 4f at its forward end as shown in FIG. 4, a shallower depth portion 4g directly, rearwardly of it, and a still shallower depth portion 4h directly rearwardly of the latter, terminating at its rear end in a transverse slot 4j for mounting the locking lever. This transverse slot 4j is most clearly shown in FIG. 3. As shown therein, slot 4j extends to the right into spring groove 42 and also downwardly almost to the bottom of the trigger.

Referring now to FIG. 6, it will be seen how locking lever 14 fits into the slot just described. This locking lever is a generally L-shaped strip having the heel portion 14a notched out to clear the spring groove in the trigger. Also, the foot portion 14b of this lever is bent less than at the ankle 14c laterally to the right so it can be pressed into slot 4j with the toe portion 14d going down to the bottom of such slot and snugly held therein. As a result, the elongated main portion of lever 14 extends as a cantilever beam forwardly in a horizontal direction with the strip being in a vertical plane at a small angle to the left. At an intermediate point on the left surface of this strip there is provided a raised rivet or round upset portion l4e serving as a catch by entering hole 6c in the frame when the trigger is in its off position. As shown in FIG. 4, there may also be provided a very small angle bend 14f to the right in the elongated portion of the locking lever directly to the rear of catch Me to afford full entry of catch 14e within hole 60.

As willbe apparent, when the rear end portion 14b is rigidly confined within slot 4 in the trigger, the elongated forwardly extending main portion of the locking lever is biased to the left by virtue of the less than 90 bend at ankle 140. The locking lever is made of suitable metal capable of spring action at bend 14c and being stiff enough to rigidly lock the trigger against moving.

The manual release means comprises a release button 16 similar to the conventional on lock button used in trigger switches. This release button is mounted within a sleeve 6d, the latter being rigidly secured over a hole in the left side of the frame at the vertical level of the forward end portion of locking lever 14. This release button is attached to a shaft 16a that extends through the mounting sleeve and hole in the frame, and a helical compression spring, not shown, but similar to that shown in FIG. 8, surrounds this shaft to bias the release button outwardly, toward the left. The right or inner end of such shaft is coined larger than its hole in the frame to secure the release mechanism to the frame.

A will be apparent, when the user presses the release button, the inner end of the shaft bends the locking lever into slot 4f 14g 4h of the trigger so that catch 42 clears hole 60 as shown in FIG. 5. While the release button is so held, the trigger may be depressed. After the trigger is slightly depressed, the release button may be released. Subsequently release of the trigger allows spring 8 to return the trigger to its off position, and upon arriving thereat, catch 14e snaps into hole 6 c to lock the trigger off. This prevents accidently starting of the portable tool as a safety measure, particularly in the case of circular saws, chain saws and the like.

The second embodiment shown in FIGS. 7-9 differ from the first embodiment in that the locking plate is carried by the release button rather than by the trigger and the abutment or lockingcatch is on the trigger rather than on the frame. As shown in FIG. 8, trigger 20 is provided with a recess in its left side at the forward portion of its slidable portion. This recess is generally horizontally rectangular in a vertical plane and has a first forward length 20a at the left surface of the trigger and a longer forward length 20b at a greater depth. This first forward length is substantially coextensive with a generally rectangular locking plate 22 and forms an abutment for the locking plate to lock the trigger in its off position.

The locking plate is rigidly secured to a shaft 22a having a helical compression spring 24 surrounding it, the shaft terminating in a manual release button 22b. A sleeve 6d surrounds spring 24 and a portion of button 22b to guide them. Except as herein noted, the frame, base and trigger may be similar to those described in connection with the first embodiment. The locking 4 plate and shaft secured thereto are most clearly shown in FIG. 9.

As will be apparent, spring 24 biases the release button outwardlyso that the locking plate abuts first forward length 20a of the slot to lock the trigger in its off position. Depression of manual release button 22b against the force of spring 24 results in the locking plate being moved within longer forward length 20b of the slot as shown in dotted lines in FIG. 8. While the release button is so held, the trigger may be depressed to on position. Upon slight depression of the trigger, the release button may be released. Upon release of the trigger, spring 8 returns the trigger to its off position and plate 22 snaps back into locking position.

The third embodiment of off locking trigger switch shown in FIGS. 10-13 is of the overhanging trigger type. As shown therein, the switch is provided with an insulating base 30 and a metal frame 32 supporting a trigger 34. The trigger is pivotally supported on the frame by a first rivet 36 at the upper right-hand portion of the trigger according to FIG. 10. A second rivet 38 at the lower right-hand portion of the trigger pivotally connects an elongated switch actuator 40 to the trigger. A helical tension spring 42 is hooked at its left end onto the frame and is coupled at its right end through an anchor pin 44 to the trigger. I

As shown in FIGS. 10 and 11, the base is a generally rectangular housing having an open top and terminals (not shown) preferably at opposite ends for connecting the switch contacts housed therein to an external circuit. An insulating plate 30a covers the base and is provided with a suitable opening through which the switch is actuated.

Frame 32 is generally inverted U-shaped substantially throughout the left half overlying the base to provide a guiding channel for longitudinally movable, elongated switch actuator 40 that extends from about the center of the base all the way to rivet 38. The right half of the frame is also inverted U-shaped as shown in FIGS. 11 and 13 but of increasing height towards the right end thereof as shown in FIG. 10. A skirt 32a hangs down from the rear side of the frame as seen in FIGS. 10 and 11 and is provided with a pair of holes 32b whereby the switch may be mounted into the handle of a portable tool.

The trigger 34 is also of inverted U-shaped construction but wider than the frame as shown in FIGS. 11-13 so that it embraces and pivots freely on the right-hand end portion of the frame. The right-hand edges of the trigger are provided with aligned notches 34a for retaining the reduced diameter end portions of anchor pin 44. The center portion of the anchor pin may be provided with a reduced-tapered section for centering the hook of the trigger-return springThe left end of the spring is hooked in a hole in the frame and the frame is provided with an elongated aperture 32c along the top thereof toward the right from this hole to afford clearance for the spring.

The off locking mechanism comprises a spring-biased locking member mounted on the frame and comprises suitable apertures in the trigger for locking the trigger and for allowing movement of the trigger when the off lock is released. This spring-biased locking member comprises a lock pin 36 having an oblong locking plate 38 rigidly secured at one end to one end thereof as by riveting or the like as shown in FIG. 12. The other end of this look pin is inserted through the trigger and frame as follows. It is first inserted through generally oblong hole 34b in the right side of the trigger, then through a round hold 32d in the right side of the frame, then through a round hole 32e in the left side of the frame, and finally through a slightly arcuate oblong hole 346 in the left side of the trigger.

As will be apparent, round holes 32d and 32e in the sides of the frame support the lock pin for axial sliding movement. Hole 34c in the left side of the trigger is a clearance hole for the lock pin to allow pivotal movement of the trigger. And hole 34b in the right side of the trigger is a locking hole, coextensive with but slightly larger than locking plate 38 to allow free entry of this locking plate therein.

A helical compression spring 40 surrounds the part of the lock pin extending out through hole 340 and a release button 42 is secured to said other end of the lock pin to place return spring 40 under an initial compression. As will be apparent, spring 40 biases the locking member into locking position.

The area immediately surrounding hole 32d in the right side of the frame is upset inwardly to provide space for the flange 36a integrally formed on the lock pin against which the locking plate is secured.

To prevent the locking plate from rotating out of place which would prevent engagement of the lock, the trigger is provided with a pair of guiding ridges 34d, one on each side of locking hole 341;.

When the trigger is released, return spring 42 normally biases it in its off position shown in FIG. 10. As a result, return spring 40 biases the locking member into its locking position with locking plate 38 having entered lock hole 34b. Under this condition, the trigger cannot be depressed.

To release the lock, the users thumb depresses the release button against the force of'return spring 40 as shown in dotted lines in FIG. 13. As a result, the lock pin lifts the lock plate clear of hole 34b as shown in dotted lines in FIG. 13, thus allowing pivotal depression of the trigger to on position. After the trigger is slightly depressed, the release button may be released as plate 38 can no longer enter the locking hole in the trigger. When the trigger is released, spring 42 returns the trigger to off position, and spring 40 snaps the lock into reengagement.

While the several modifications of the apparatus hereinbefore described are effectively adapted to fulfill the objects stated, it is to be understood that the invention is not intended to be confined to the particular preferred embodiments of off locking trigger switches disclosed, inasmuch as they are susceptible of various modifications without departing from the scope of the appended claims.

I claim:

1. A self-enclosed trigger switch for a portable electric tool affording operation of the tool but preventing accidental operation thereof comprising;

an insulating base housing the switch mechanism;

a movable spring-biased trigger forming a first part and having a normal off position in which the tool is not in operation and having an alternate on position in which the tool is in operation;

a frame forming a second part and mounting said trigger for movement relative to said base and frame and means coupling said trigger to the switch mechanism to allow operation thereof;

and an automatically-engaging off lock for said trigger comprising;

a resiliently-biased locking member coupled between said movable trigger and said frame parts and means mounting said locking member on one of said parts and locking catch means operative between said locking member and the other part;

said mounting means comprising means supporting said locking member on said one part for limited movement relative thereto, and means resiliently biasing said locking catch means toward locking engagement with said other part, and being movable within said limited movement to disengage said locking catch means from said other part;

a release button depressible against the force of said resilient bias means to disengage said catch means thereby to allow movement of said trigger from its off to its on position;

and said resilient bias means causing automatic reengagement of said catch means when said trigger is released and returned to its off position.

2. The invention defined in claim 1, wherein said resiliently-biased locking member, mounting means and locking catch means comprises:

a spring-biased pin mounted for limited axial move ment on said frame;

an eccentric locking plate attached to one end of said a release button attached to the other end of said pin;

a compression spring on said pin between said frame and said release button;

and a stop wall formed on said trigger in alignment with the eccentricity of said locking plate and the axis of said pin behind which said eccentric locking plate is snapped by said compression spring whenever said trigger returns to its off position, said alignment causing the force oftrigger pull to be applied directly to the axis of said pin when said trigger is locked without any torque being applied thereto through said eccentricity;

and depression of said release button against the,

force of said compression spring causes said eccentric locking plate to move clear of said stop wall to allow movement of said trigger.

3. The invention defined in claim 2, wherein:

said trigger is an in-line trigger mounted for linear sliding movement along the top of said base;

and said stop wall is formed by a stepped slot in said trigger having an initial short dimension providing said stop wall abutting said locking plate in the undepressed position of the latter and also having an adjacent longer dimension providing clearance for said locking plate in the depressed position of the latter to allow operation of the trigger.

4. The invention defined in claim 2, wherein;

said trigger is an overhanging trigger mounted for pivotal movement on said frame;

and said stop wall is formed by a-hole in one side of said trigger complementary to said locking plate to freely receive said locking plate and into which said locking plate snaps whenever the trigger returns to its off position and depression of said release button moves said locking plate out of said hole to permit trigger operation.

5. A self-enclosed trigger switch for a portable electric tool affording operation of the tool but preventing accidental operation thereof comprising:

an insulating base housing the switch mechanism;

a movable spring-biased trigger having a normal off position in which the tool is not in operation and having an alternate on position in which the tool is in operation;

a frame mounting said trigger for movement relative to said base and frame and means coupling said trigger to the switch mechanism to allow operation thereof;

and an automatically-engaging off lock for said trigger comprising:

a resiliently-biased locking member coupled between said movable trigger and said frame and means mounting said locking member to one thereof and locking catch means between said locking member and the other thereof;

a release button depressible against the force of said resilient bias to disengage said catch means thereby to allow movement of said trigger from its off to its on position;

and said resilient bias causing automatic reengagement of said catch means when said trigger is released and returned to its off position;

said resiliently-biased locking member, mounting means and locking catch means comprising:

a leaf spring mounted at one end in a slot in said trigger and being formed with an outward bias to bias the other end portion thereof against said frame and including a projecting catch on said other end portion;

and a hole in said frame located so as to receive said catch under the force of said bias whenever said trigger returns to its off position to lock the latter therein.

6. The invention defined in claim 5, wherein said release button comprises:

a spring-biased button including a pin mounting the same in a hole in said frame for limited axial movement therein and being located in registration with said other end portion of said leaf spring so that depression of said button causes said pin to move said projecting catch clear of said hole in said frame to allow movement of said trigger.

7. A trigger switch for a portable electric tool affording intended operation thereof but automatically locking it against accidental operation whenever the switch is released comprising;

a housing for the switch mechanism;

a trigger mounted on said housing for limited reciprocal movement between an on position wherein the switch is in operation and an off position wherein the switch is not in operation;

a return spring normally biasing said trigger into its off position;

and an automatically engaging off lock for said trigger including;

a spring-biased locking member coupled between said housing and said trigger, being mounted to and movable with the trigger and being engagable and disengagable with respect to the housing, engagable to lock the trigger against movement with respect to the housing and disengagable to allow trigger movement with respect to the housing;

said engagement and disengagement being provided by a catch and an abutment, said catch being movable with trigger movement and said abutment being stationary with said housing;

said catch and said abutment being located so that said spring bias causes automatic engagement between said catch and said abutment whenever said trigger is returned to its off position to prevent accidental operation of said switch;

and a release button mounted on said housing and being depressible to separate said catch from said abutment to allow operation of said trigger to its on position.

8. In combination with a portable tool having a handle to be grasped by the right hand of the user, an aperture in the front of the handle for a trigger and a hole in the left side of the handle for an off lock release button;

a self-enclosed trigger switch mounted within said handle comprising;

a housing for the switch mechanism;

a trigger mounted on said housing for limited movement between an on position wherein the switch is in operation and an off position where the switch is in operation;

said trigger extending out of said aperture for depression by the forefinger of the user;

a return spring normally biasing said trigger into its off position;

and an automatically engaging off lock for said trigger including;

a spring-biased locking member between said housing and said trigger, being unitarily associated with said trigger with the spring being between said locking member and said trigger and being engagable and disengagable with respect to said housing, engagable to lock the trigger against movement with respect to the housing and disengagable to allow trigger movement with respect to the houssaid engagement and disengagement being provided by a catch and an abutment, said catch being movable with trigger movement and said abutment being stationary with said housing;

said catch and said abutment being located so that said spring bias causes automatic engagement between them whenever said trigger is returned to its off position to prevent accidental operation of said I tool;

and a release button mounted on said housing and extending out of said hole in said handle to be depressible by the thumb of the user to separate said catch from said abutment to allow operation of said 

1. A self-enclosed trigger switch for a portable electric tool affording operation of the tool but preventing accidental operation thereof comprising; an insulating base housing the switch mechanism; a movable spring-biased trigger forming a first part and having a normal off position in which the tool is not in operation and having an alternate on position in which the tool is in operation; a frame forming a second part and mounting said trigger for movement relative to said base and frame and means coupling said trigger to the switch mechanism to allow operation thereof; and an automatically-engaging off lock for said trigger comprising; a resiliently-biased locking member coupled between said movable trigger and said frame parts and means mounting said locking member on one of said parts and locking catch means operative between said locking member and the other part; said mounting means comprising means supporting said locking member on said one part for limited movement relative thereto, and means resiliently biasing said locking catch means toward locking engagement with said other part, and being movable within said limited movement to disengage said locking catch means from said other part; a release button depressible against the force of said resilient bias means to disengage said catch means thereby to allow movement of said trigger from its off to its on position; and said resilient bias means causing automatic reengagement of said catch means when said trigger is released and returned to its off position.
 2. The invention defined in claim 1, wherein said resiliently-biased locking member, mounting means and locking catch means comprises: a spring-biased pin mounted for limited axial movement on said frame; an eccentric locking plate attached to one end of said pin; a release button attached to the other end of said pin; a compression spring on said pin between said frame and said release button; and a stop wall formed on said trigger in alignment with the eccentricity of said locking plate and the axis of said pin behind which said eccentric locking plate is snapped by said compression spring whenever said trigger returns to its off position, said alignment causing the force of trigger pull to Be applied directly to the axis of said pin when said trigger is locked without any torque being applied thereto through said eccentricity; and depression of said release button against the force of said compression spring causes said eccentric locking plate to move clear of said stop wall to allow movement of said trigger.
 3. The invention defined in claim 2, wherein: said trigger is an in-line trigger mounted for linear sliding movement along the top of said base; and said stop wall is formed by a stepped slot in said trigger having an initial short dimension providing said stop wall abutting said locking plate in the undepressed position of the latter and also having an adjacent longer dimension providing clearance for said locking plate in the depressed position of the latter to allow operation of the trigger.
 4. The invention defined in claim 2, wherein; said trigger is an overhanging trigger mounted for pivotal movement on said frame; and said stop wall is formed by a hole in one side of said trigger complementary to said locking plate to freely receive said locking plate and into which said locking plate snaps whenever the trigger returns to its off position and depression of said release button moves said locking plate out of said hole to permit trigger operation.
 5. A self-enclosed trigger switch for a portable electric tool affording operation of the tool but preventing accidental operation thereof comprising: an insulating base housing the switch mechanism; a movable spring-biased trigger having a normal off position in which the tool is not in operation and having an alternate on position in which the tool is in operation; a frame mounting said trigger for movement relative to said base and frame and means coupling said trigger to the switch mechanism to allow operation thereof; and an automatically-engaging off lock for said trigger comprising: a resiliently-biased locking member coupled between said movable trigger and said frame and means mounting said locking member to one thereof and locking catch means between said locking member and the other thereof; a release button depressible against the force of said resilient bias to disengage said catch means thereby to allow movement of said trigger from its off to its on position; and said resilient bias causing automatic reengagement of said catch means when said trigger is released and returned to its off position; said resiliently-biased locking member, mounting means and locking catch means comprising: a leaf spring mounted at one end in a slot in said trigger and being formed with an outward bias to bias the other end portion thereof against said frame and including a projecting catch on said other end portion; and a hole in said frame located so as to receive said catch under the force of said bias whenever said trigger returns to its off position to lock the latter therein.
 6. The invention defined in claim 5, wherein said release button comprises: a spring-biased button including a pin mounting the same in a hole in said frame for limited axial movement therein and being located in registration with said other end portion of said leaf spring so that depression of said button causes said pin to move said projecting catch clear of said hole in said frame to allow movement of said trigger.
 7. A trigger switch for a portable electric tool affording intended operation thereof but automatically locking it against accidental operation whenever the switch is released comprising; a housing for the switch mechanism; a trigger mounted on said housing for limited reciprocal movement between an on position wherein the switch is in operation and an off position wherein the switch is not in operation; a return spring normally biasing said trigger into its off position; and an automatically engaging off lock for said trigger including; a spring-biased locking member coupled between said housing and said Trigger, being mounted to and movable with the trigger and being engagable and disengagable with respect to the housing, engagable to lock the trigger against movement with respect to the housing and disengagable to allow trigger movement with respect to the housing; said engagement and disengagement being provided by a catch and an abutment, said catch being movable with trigger movement and said abutment being stationary with said housing; said catch and said abutment being located so that said spring bias causes automatic engagement between said catch and said abutment whenever said trigger is returned to its off position to prevent accidental operation of said switch; and a release button mounted on said housing and being depressible to separate said catch from said abutment to allow operation of said trigger to its on position.
 8. In combination with a portable tool having a handle to be grasped by the right hand of the user, an aperture in the front of the handle for a trigger and a hole in the left side of the handle for an off lock release button; a self-enclosed trigger switch mounted within said handle comprising; a housing for the switch mechanism; a trigger mounted on said housing for limited movement between an on position wherein the switch is in operation and an off position where the switch is in operation; said trigger extending out of said aperture for depression by the forefinger of the user; a return spring normally biasing said trigger into its off position; and an automatically engaging off lock for said trigger including; a spring-biased locking member between said housing and said trigger, being unitarily associated with said trigger with the spring being between said locking member and said trigger and being engagable and disengagable with respect to said housing, engagable to lock the trigger against movement with respect to the housing and disengagable to allow trigger movement with respect to the housing; said engagement and disengagement being provided by a catch and an abutment, said catch being movable with trigger movement and said abutment being stationary with said housing; said catch and said abutment being located so that said spring bias causes automatic engagement between them whenever said trigger is returned to its off position to prevent accidental operation of said tool; and a release button mounted on said housing and extending out of said hole in said handle to be depressible by the thumb of the user to separate said catch from said abutment to allow operation of said tool. 